Process for the manufacture of nicotinic acid



Patented Nov. 13, 1945 UNITED STATES PATENT OFFICE PROCESS FOR THE MANUFACTURE OF NICOTINIO ACID John Lee, Nntley, N. 1., and Stephen D. Heineman, New York, N. Y., asslgnors to Hoffmann-La Roche Inc., Nutley, N. J., a corporation of New Jersey No Drawing. Application September 24, 1941, Serial No. 412,157

4 Claims. (Cl. 260-2955) 1 mol of carbon dioxide and gradually forms a solid mass of nicotinic acid which melts at 230 C. Thi method is useless for technical purposes, since it yields an inhomogeneous fusion mass which, moreover, is discolored and still contains all the impurities inherent in the crude quinolinic acid.

It was found by S. Hoogewerfi and others (Ber. 14, 974, 1884) that decarboxylation can be effected by boiling the pyridine carboxylic acid, such as quinolinic acid, in glacial acetic acid at its boiling point of 118 C. Quinolinic acid is soluble in the glacial acetic acid, but in order to effect complete decarboxylation it is necessary to reflux the solution for a considerable period of time, and in order to recover the nicotinic acid, the solution must be evaporated. It is apparent, therefore, that this method is expensive since it requires considerable time and heating costs. Moreover, the glacial acetic acid used is extremely corrosive to the usual types of chemical manufacturing equipment.

It is, thus, an object of the present invention to provide a decarboxylation method which operates at high velocity and effects the reaction in a comparativel short period of time, thus increasing the efliciency of a given piece of equipment and cutting the overhead and the heating costs. It is a further objectto provide a means for decarboxylating at comparatively low temperatures, such as are readily accessible by use of low pressure steam, and thus, economizing in construction and heat costs.

.A further object is to provide a method which can operate in the usual manufacturing laboratory equipment without any special precautions and without corrosion of the vessel occurring and without any contamination of nicotinic acid occurring, due to the metallic impurities.

Another object is to avoid tediou evaporations of liquor to crystallize out the nicotinic acid formed and to obtain high yields'of the acid.

A further object is to remove colored impurities from the crude quinolinic acid so as to obtain in one operation substantially pure nicotinic acid.

We have now found that the disadvantages of prior methods can be avoidedand the objects of our invention be satisfied ifdecarboxylation is efiected by heat treatment in glycerine, glycols or ethylene glycol alone or more preferably in the presence of an indifferent organic liquid in which both nicotinic acid and quinolinic acid are substantially insoluble or in which at least the nicotinic acid is substantially insoluble at room temperature.

We have found that such indifferent liquids, i. e. liquids which do not react chemically with quinolinic or nicotinic acid, are suitably hydrocarbons of the benzenoid and naphthenoid series and the esters of acids containing benzenoid or naphthenoid nucleus.

In most of these solvents the most effective decarboxylation occurs between and C., but may start slowly as low as 110 C., slightly higher temperatures being necessary with the hydrocarbon materials other than xylene to effect a satisfactory decarboxylation rate.

In particular, we have found that a mixture of the hydrocarbon solvent and of the glycol miscible therewith, offers several advantages over the hydrocarbon solvent alone.

Decarboxylation in that case occurs at a rather low temperature, the velocity of reaction is higher than that obtained with hydrocarbon alone, and the retention of the impurities is improved. Furthermore, the mixture retains practically no nicotinic acid in solution, and no difliculties in filtering the decarboxylated reaction mixture are encountered if the solution is filtered at a temperature at which the components are miscible.

Thus, we have discovered that a mixture of xylene and nona-ethylene glycol at the temperature of about 130 C. develops an exceptionally good decarboxylating effect, and that the yields of nicotinic acid are quantitative. This is distinctly surprising, since it was to be expected that decarboxylation in a material in which quinolinic acid is particularly insoluble, would require temperatures approaching the melting point of quinolinic acid at 195 C. on the theory that the liquid would surely act a a heat transfer agent. That this is not so, contrary to expectation, is indicated by the fact that on heating the quinolinic acid at C. with liquid petrolatum no decarboxylation occurs. Moreover, when heating in direct heat transfer agents like liquid petrolatum,

even as low as 160 0., extensive carbonization occurs.

Other solvent containing the benzene nucleus which have this decarboxylating efl'ect-were found to be esters of phthalic acid, and the like. These The range other the advantage that they can be mixed in various proportions with the glycols which have a considerably greater decarboxyiating efi'ect to give solvent mixtures in which the nicotinic acid is comparatively insoluble, which, nevertheless, decarboxylate rapidly at about 130 to'140 C. of glycols that may be used with the esters is rather extensive since the class of glycols generally is more soluble in the esters than in the hydrocarbons.

We have found that a lower boiling hydrocarbon, such as toluol, B. P. 111 C., which alone has no significant decarboxylating eilect, can, at the temperature at which it normally boils, be made to decarboxylate quinolinic acid at an appreciable rate by the addition of a suitable amount of a glycol. A 1:1 mixture of nonaethylene glycol and toluene is such.

Furthermore, we have found that we may advantageously use a mixture of glycol,an ester and a hydrocarbon. In this case a miscible decarboxylating liquid can be obtained containing a higher proportion of a glycol than would be possible using a mixture of a glycol and a hydrocarbon alone. For example, a mixture of 2 parts nona-ethylene glycol and 8 parts xylol are not completely miscible at room temperature but the addition oi 1 part 01 butylphthalate gives a coinpletely miscible mixture. Such a mixture has a rapid decarboxylating action, a solvent capacity for impurities and filters with ease.

In the foregoing description of our invention.

by a liquid hydrocarbon we mean a cylic hydrocarbon of the class of benzene homologs with 8 or more carbon atoms such as the xylols, diethylbenzenes and other substituted benzenes such as those commercially known as the alkazenes, liquid hydrogenated naphthalene hydrocarbons such as tetrahn and decalin. By an ester we mean aliphatic esters of acids containing a benzenoid or naphthenoid nucleus such asbenzoic acid, phthalic acid, naphthalene carboxylic acid and the like, as for example, methyl benzoate, isopropyl benzoate, dimethyl phthalate, dibutyl phthalate, ethyl-a-naphthalene monocarboxylate.

By a glycol we mean glycol and its homologs such as propylene glycol and also diethylene glycol and its homologs such as triethylene glycol, tetraethylene glycol and nonaethylene glycol.

By a miscible glycol we mean a glycol miscible with the above mentioned hydrocarbon solvents at least at temperatures above 60 C.

By a glycerin we mean glycerin and its monoesters which are liquid above 115 C., such as glycerin monochlorhydrin, glyceryl monoacetate. ti The following examples illustrate our inven- Example 1 parts by weight of quinolinic acid and "1 parts by volume diethylene glycol are heated at 135 to 140 until CO: evolution ceases after about 30 minutes. The mixture can be filtered directly or diluted with a small amount of cold ethylacetate and filtered. Nicotinic acid is obtained in a yield of 84%.

Example 2 g 5 parts by weight of quinolinic acid and 4 parts by volume triethylene glycol are heated to 125 for 35 minutes, cooled, diluted with 5 parts by volume cold ethylacetate and filtered. The yield ofnicotinic acid is 88%.

Example 3 5 parts by weight of quinolinic acid and 6 parts by volume nonaethylene glycol are heated to 145 for minutes, cooled, diluted with benzol and filtered. A yield of nicotinic acid of 94% is obtained as colorless or faintly bufl tinted v crystals.

Example 4 6 parts of quinolinic acid and 8 parts dipropylene glycol are heated to 130 C. When the evolution of CO2 is completed in 30 minutes, 10 parts of cold ethylacetate are added and the mixture filtered and the nicotiniclacid washed with ethyl acetate. Yield 96%.

Example 5 A mixture of 2 parts nonaethylene glycol, 8 parts technical xylol, 1 part butyl phthalate and 5 parts quinolinic acid are heated under reflux with stirring to 115-435 C. Decarboxyiation begins at about and is brisk at C. At it is very rapid. After decarboxylatlon is complete, which required from 15 minutes to 2 hours according to the temperature and size of the batch, the liquid is cooled and the nicotinic acid filtered off under suction. The nicotinic acid is washed on the filter with a little benzol and then dried. The yield is quantitative.

Example 6 5 parts of quinolinic acid are suspended in a mixture of 2 /2 parts of toluol and 2 /2 parts nonaethylene glycol. This mixture is refluxed until CO: evolution ceases, cooled and the nicotinic acid filtered 011.

What we claim is:

1. In a process for the manufacture of nicotinic acid, the steps of heating quinolinic acid in an indifferent liquid medium selected om the group consisting of nonaethylene glycol and a mixture of toluol with a substantial amount of nonaethylene glycol, in which medium nicotinic acid is substantially insoluble at room temperature, within the temperature range of from 110 to 135 C. until the evolution of carbon dioxide ceases, cooling the medium, and recovering the nicotinic acid thus produced.

2. In a process for the manufacture of nicotinic acid, the steps of heating quinolinic acid in a mixture of toluol and nonaethylene glycol, containing a substantial quantity of the latter, within the temperature range of from 110 to 135 C. until the evolution of carbon dioxide ceases. cooling the mixture, and recovering the nicotinic acid thus produced.

3. In the process of decarboxylating quinolinic acid into nicotinic acid by heating in a decalboxylating medium, the step which comprises heating the initial material in nonaethyleue glycol to 135 C. until the evolution of carbon dioxide ceases, cooling the mixture, diluting it with benzol and filtering the precipitate.-

4. In the process of decarboxylating quinolinic acid .into nicotinic acid in a decarboxylating medium, the step which comprises heating the quinolinic acid within a temperature-range between 110 and C. in a composition comprising a polyhydroxy aliphatic alcohol admixed with a substance selected from the group consisting of benzenoid and naphthenoid hydrocarbons, and continuing the heating in said temperature range until the evolution of carbon dioxide ceases, and recovering the nicotinic acid thus produced.

JOHN LEE. STEPHEN D. H'EINEMAN. 

